A current OLED panel, which possesses self-luminous organic electroluminescent photodiodes requiring no backlight and has excellent properties such as high contrast, thin thickness, broad viewing angles, rapid response, applicability in a flexible panel, wide temperature applications and relatively simple construction and manufacture procedures, is considered as a next-generation flat panel display technology. Although the OLED panel has so many advantages, the OLED panel has a shorter service lifetime than an LCD panel, because the OLED panel is a current-driven self-luminous body of which the material and component lifetime have higher requirements for power supply. The current grid voltage is subjected to certain fluctuations which may cause instability or even overvoltage in the power supply. It is therefore needed to protect the circuit of the OLED panel and especially provide accurate and rapid overvoltage protection for the power supply of the OLED panel, and maintain power supply stability, thereby better protecting the display panel.